Discussion of the dissertation well be held 10.October.1985, at 10.00 a.m. at the meeting of the special neurosurgical committee D 084.23.01 in Leningrad Research Institute of Neurosurgery of Prof. A. L. Polenov. (191104. Leningrad, Mayakovskaya Street, 12).

The dissertation material can be obtained from the library of the Leningrad Research Institute of Neurosurgery of Prof. A. L. Polenov.

The abstract was published in 10.September.1985

Secretary of Special Neurosurgical Committee

Tayushev K.G. Ph. D

INTRODUCTION

The actual importance of the present work: Surgery of the pituitary adenomas with massive extrasellar extension, is one of the most important problems in neurooncology. The huge number of patients with pituitary adenomas with massive extrasellar extension, the young age of these patients, and the ability for complete recovery after delicate radical subcapsular excision of these tumors; All these factors reflect the importance of this scientific work. During the last 10 years, surgery of the pituitary adenomas was discussed in the II and III Neurosurgical Congresses in USSR (1976, 1982), the VII International Congress of Neurosurgery (1981), and the Plenum of Problematic Comity `Neurosurgery` USSR (1984). The still unacceptable results of surgical treatment of pituitary adenomas with massive supra-retro-parasellar extension, attracted the constant attention of many neurosurgeons.

In the last decade, many technical standards evolved in the treatment of pituitary adenomas. These changes are intimately related with the advancement of new diagnostic capabilities, preoperative planning, the introduction of new adequate surgical approaches , microsurgical instrumentation and postoperative care. Despite, that, the problem remains far enough from its complete resolution (Konovalov A. N. et al 1984). This problem is one of the most important in the VIII International Congress of Neurosurgery.

In the literature, there are many reports about the surgical treatment of pituitary adenomas with extrasellar extension through Transsphenoidal route ( Hoi S. et al., 1977; Laws E. et al., 1979; Ciric I. Et al., 1983; Pasztor E. et al., 1983; Nelson A. et al., 1984). These approaches are not acceptable for the surgical removal of the invasive, hard in consistency, tumors with massive extrasellar extension. For that reason, the subfrontal approach is still the golden standard in removal of pituitary adenomas with massive extrasellar extension. Considering that, in most neurosurgical departments these patients with massive extrasellar extension still coming for treatment. Removal of these tumors is preferred by subfrontal route ( Melkishev V.F. 1981; Symon L. et al., 1979; Bergland R., 1984).

Introduction and refinement of the bifrontal approach with ligation and section of the superior sagittal sinus at the crista Galli , proposed by Pool J. 1957, to the Leningrad Research Institute for Neurosurgery and other major neurosurgical centers in USSR dramatically improved the results of surgical treatment of pituitary adenomas , including the giant ones ( Romodanov A. P., Zozulya Y. A., 1974; Konovalov A. N., 1976; Tigliev G.S., 1977): Postoperative mortality, according to the material of Leningrad Research Institute for Neurosurgery , decreased to 7.4% (1981). The ability of this approach to offer to the surgeon good visualization of all vital structures, and their relation to the supra-retro-antesellar extensions of the tumor, with subsequent, more radical save excision is the reason for better outcome.

Nevertheless, with more experience acquired, the negative drawbacks of this approach became evident : bilateral anosmia due to olfactory tracts section in all patients undergoing this procedure, massive widespread basal arachnoiditis of the cortex of both frontal lobes . It became clear also, that the excellent widespread visualization of the chiasmo-sellar region by this bifrontal approach to be obtained by other more narrow-angled subfrontal approaches, such as the monofrontal approach, is impossible in certain circumstances.

Objectives of the investigation

The aim of the present dissertation is the creation of new more physiologic modifications of subfrontal approaches, which must be able to give adequate visualization of the neoplasm during surgical excision of the pituitary adenoma with massive extrasellar extension

To achieve this aim, an investigation was introduced with the following clear-cut objectives:

nintroduction of new modifications of subfrontal route with simultaneous anatomical preservation of the intracranial part of the peripheral division of the olfactory system, with improvement of the neoplasm visualization.

nevaluate the degree of surgical trauma after mobilization of the olfactory tracts down to the trigones.

nevaluate the adequacy of different subfrontal approaches by electrophysiological control during operation, and the degree of functional neurological recovery (first of all the visual) of the preoperative deficits in the immediate postoperative period, and the olfactory function, using the method proposed by Bernstein.

New data, acquired in the investigated problem. A new complete system with different modifications of subfrontal approaches is proposed , taking into account the volume and the direction of the tumor growth and its relation to the surrounding vital structures of the brain. It was possible to demonstrate the superiority of the new modifications of subfrontal approaches with simultaneous mobilization and anatomical preservation of the olfactory tracts in the surgery of pituitary adenomas with massive extrasellar extension upon the previously suggested approaches. These data were reflected by the degree of visual recovery and preservation of the olfactory function in the immediate postoperative period.

The practical value of the investigation. The differential use of the suggested new subfrontal approaches in the surgical treatment of pituitary adenomas with massive extrasellar extension with the use of microsurgical technique, made it possible to obtain practical absence of postoperative mortality, improvement of the degree of visual functional recovery and preservation of olfactory function in the immediate postoperative period.

The essential scientific conclusions forwarded in the discussion of the dissertation:

1. Proposed new modifications of subfrontal approaches with simultaneous preservation of the anatomical olfactory integrity in the majority of the operated patients yielded preservation of olfactory function in high percent of patients.

2. Differential use of suggested modifications of subfrontal approaches with simultaneous mobilization and anatomical preservation of the olfactory tracts ( monofrontal, bifrontal with ligation and section of the superior sagittal sinus at the crista Galli , bifrontal with section of the falx cerebri at the crista Galli with preservation of the continuity of the superior sagittal sinus ) , gave adequate visualization of the tumor during its microsurgical removal.

3. Correlative evaluation of surgical results of patients operated upon by standard and new subfrontal modifications demonstrate clearly the positive effects of the later modifications.

Implementation . The new system of subfrontal approaches in the surgery of pituitary adenomas with massive extrasellar extension , became the usual technical standard in the departments of Leningrad Research Institute of Neurosurgery . The material of the dissertation underwent with the educational program of the 1st Leningrad Medical Institute of acad. Pavlov IMP., the Sanitaro-hyegene Medical Institute and the Len GIDUV. Of Kirov S. M. and the department of neurosurgery in Krasnoyarsk Medical Institute.

Approbation of the material. The material of the dissertation was announced in the preliminaries of the Leningrad Neurosurgical Community ( Mart.1983 ; mart 1985 ) . One publication was deposited in VNIMII No D 9605,3.6.85. Authority of this new system under the number of 1153892 SU was achieved and published in the Bulletin No. 17,07.05.85, and one certificate for rationalization proposal .

The structure and volume of the dissertation. The dissertation consists of introduction, five chapters , discussion, results, references and appendix. The dissertation is written in 182 pages of typewriting, of them 104 pages-textual, 19 figures and 23 tables. There are 331 references; 119 Russian and 212 in foreign languages.

THE SUBJECT MATTER

Material and method . There is comparative analysis of two groups of patients with pituitary adenomas with massive extrasellar extension , operated upon in the Leningrad Research Institute for Neurosurgery of Polenov A. L. during the period 1979 -1985. Group A - 65 cases operated by the new approaches and group B - 66 cases by traditional means. 59.5% of the all patients were female; the main age was 41.07±13.5 years. By the degree of suprasellar extension , tumors were divided into three groups : 1.tumors with mild suprasellar extension: the suprasellar pole was 10 mm or more above the planum sphenoidale and less than 20 mm, without considering the degree of infrasellar extension; 2.tumors with moderate suprasellar extension , more than 20 mm above the level of the planum sphenoidale ; 3. Giant tumors with diameter not less than 45 mm, or with suprasellar extension more than 40 mm above the level of planum sphenoidale with parasellar extension.

CONCLUSION

1. Proposed new modifications of subfrontal approaches with simultaneous anatomical preservation of the intracranial part of the olfactory system yielded adequate visualization and conditions for surgical manipulations during removal of pituitary adenomas with massive extrasellar extension.

2. So as to preserve the anatomical and functional integrity of olfaction, it is mandatory to mobilize the olfactory tract down to the olfactory triangle in the ipsilateral side and the olfactory bulb in the contralateral side , during the monofrontal subfrontal approach. In the case of bifrontal route , it is necessary to mobilize both olfactory tracts down to their triangles.

3. Electrophysiological data during operative intervention and neurological dynamics after mobilization of the olfactory tracts , using the microsurgical technique failed to show deleterious effects upon the basal parts of both frontal lobes , neither traumatic, nor circulatory in character.

4. Bifrontal approach to the giant pituitary adenomas is recommended only after revision of the tumor through monofrontal route. Indication for that is the hard consistency and rich vascularity of the tumor and chiasma fixa and prefixa.

5. The recommended unilateral subfrontal approach with section of the falx cerebri at the crista Galli with preservation of the integrity of the superior sagittal sinus, actually widens the field of operative intervention to be almost equal to the conditions of bifrontal approach.

6. In the comparative study of the results of surgical treatment of patients with extrasellar pituitary adenomas by the standard and modified approaches , taking into account the early postoperative period ( no mortality , considerable improvement of visual functions , practical absence of morbidity in the latter group ), it can be demonstratively seen the superiority of the modified approaches. None-the-less, despite the technical progress , the results of hormonal impairment still lacking. The majority of the patients with preoperative panhypopituitarism urging supplementary hormonal therapy usually continue in the same regimen.